The invention relates to a synthetic grass turf with infill therein to provide an artificial surface for sports and for growing vegetables and other plants, more particularly to a synthetic grass turf with integrated thermal regulation to control the thermal conditions of the artificial surface.
As is well known, the construction of a good quality all weather grass playing surface and its maintenance for recreational purposes and active sports, such as soccer and football, has been a problem of long standing.
Recent attempts at resolving this problem have resulted in the use of artificial surfaces to replace natural grass surfaces which do not stand up well to wear, and which require a great deal of maintenance. Also, natural grass surfaces do not grow well in partially or fully enclosed sports stadiums. A synthetic grass surface stands up to wear much better than the natural grass surfaces, does not require as much maintenance and can be used in closed stadiums. An improved synthetic grass surface is described in the Applicant""s Canadian Patent Application 2,218,314, entitled SYNTHETIC TURF, which was filed Oct. 16, 1997, and was published on Sep. 10, 1998. The synthetic grass surface described in this patent application comprises widely spaced rows of synthetic ribbons representing grass fibers. The ribbons have a length of about twice the length of the spacing between the rows of ribbons. A particulate material is laid on a matrix of the synthetic grass, and the thickness of the particulate material is at least two thirds of the length of the ribbons. The strips of ribbons are attached by strips of bonding material applied to the back of the matrix or mat. The strips of bonding material are spaced apart and leave an area of mat un-coated, thereby providing improved drainage.
The particulate material of the infill is further described in the Applicant""s U.S. Pat. No. 5,958,527, entitled PROCESS OF LAYING SYNTHETIC GRASS, issued on Sep. 28, 1999.
Under cold climatic conditions in open stadiums, the synthetic grass turf could be heated to melt snow or ice which covers the synthetic grass turf in order to maintain the adequate properties required for sport playing surfaces. When the synthetic grass turf is used under very warm climatic conditions, however, the cooling of the grass turf is desirable.
Heating systems have been developed for thawing and drying both natural and synthetic grass surfaces, such as electrical, fluid and air heating systems. Electrical heating is implemented by means of electrical resistance elements, fluid heating by communicating heating fluid through a network of heating pipes and air heating by communicating heated air through a distribution pipe network. Conventionally, these electrical resistance elements, fluid heating pipes and air distribution pipe networks are buried in a substrate of the playing field beneath the natural or synthetic grass turf. Examples of the electrical heating, fluid heating and air heating are described, respectively, in U.S. Pat. No. 5,046,308 which issued to Alnond et al. on Nov. 12, 1991, U.S. Pat. No. 5,120,158 which issued to Husu on Jun. 9, 1992 and U.S. Pat. No. 4,462,184 which issued to Cunningham on Jul. 31, 1984.
During warm climatic conditions, synthetic grass turf surfaces are to be cooled, conventionally, by providing moisture to the synthetic surface and circulating cool water beneath the synthetic surface. This is also described in U.S. Pat. No. 4,462,184.
Furthermore, it is also desirable to have a thermal regulating system for an artificial surface having organic growing media for growing plants in order to meet specific temperature requirements for the roots of plants.
The disadvantage of conventional heating systems lies in that a large portion of the heat energy is wasted and only a small amount of the heat energy reaches the surface for melting snow or ice coverage on the top of the surface, because the electrical resistance elements and pipe systems are buried in the playing field beneath the natural grass turf or the synthetic surfaces, usually in a substrate of the field. Therefore, a large portion of the heat energy is consumed heating the substrate while heating the surface of the playing field.
Therefore, there is a need for an artificial surface having a heating and cooling system with improved thermal efficiency.
It is one object of the present invention to provide an artificial surface with integrated thermal regulation for sports and other uses.
It is another object of the present invention to provide an artificial surface for sports and other uses which includes a heating system having improved thermal efficiency.
It is a further object of the present invention to provide an artificial surface for sports and other uses which includes a cooling system having improved cooling efficiency.
The present invention is generally directed to an artificial surface with integrated thermal regulation for sports and other uses. The artificial surface comprises a synthetic turf base including a flexible backing sheet adapted to be positioned on a support substrate. An infill layer of a particulate material is disposed upon a top surface of the flexible backing sheet. The particulate material is selected from at least one of a group of materials consisting of hard granules, resilient granules and a growth medium. The artificial surface further includes a plurality of parallel rows of synthetic ribbons representing blades of grass, projecting upwardly from the flexible backing sheet and through the infill layer. A thermal regulating means is attached to the flexible backing sheet for controllably regulating a thermal condition of the synthetic turf base, the synthetic ribbons and the infill layer.
In accordance with one aspect of the present invention, the thermal regulating means comprises a flexible electric heating element adapted to be connected to an electrical power source to convert electric current into heat energy. The flexible electric heating element according to one embodiment of the present invention is flat and can be laminated to the flexible backing sheet. In another embodiment of the present invention, the flexible electric heating element comprises an electric cable attached to the top surface of the flexible backing sheet. The electrical cable is buried under the infill layer. The electric heating element preferably has a layout which includes a majority of elongate sections extending parallel to the rows of synthetic ribbons. The respective elongate sections are disposed in spaces between the rows of synthetic ribbons, and are laminated to the flexible backing sheet. Alternatively, the respective elongate sections are bonded to the top surface of the flexible backing sheet by means of hot-melt adhesive which has an activating temperature higher than a predetermined temperature at which the electric heating element converts electric current into heat. This method can be used to convert existing sports fields with these characteristics to heated fields.
The infill layer preferably comprises a heat distributing particulate material having a relative effective conducting property. The heat distributing particulate material is disposed at the bottom of the infill layer and in contact with the thermal regulating means in order to effectively regulate thermal conditions of the synthetic base, the synthetic ribbons and the infill layer, while providing the surface with a resilient property.
In another embodiment of the present invention, the infill layer comprises soil for growing plants on the artificial surface. The synthetic ribbons retain the soil on the artificial surface against wind erosion.
In accordance with another aspect of the present invention, the thermal regulating means comprises a flexible pipe which substitutes for the electric heating element and is adapted to be connected to a water source for circulation of the water therethrough. When hot water is circulated therethrough, the flexible pipe can be used as a heating device for the artificial surface. When cool water is circulated therethrough, the flexible pipe can be used as a cooling device for the artificial surface. When it is used as a cooling device, the flexible pipe is preferably perforated, such as drip irrigation pipes, and is in fluid communication with the infill layer by means of the perforation thereof. Thus, moisture can be provided to the infill layer and thereby generates a cooling function when the moisture evaporates. The moisture is also desirable, especially when the infill layer comprises a growth medium such as soil, for plant growth. In plant growth format, a secondary backing of the grass can be non-permeable to conserve water. The amount of water dispensed in the system can be monitored to reduce the evaporation process when sprinkling systems are used.
Similar to the electric heating element, the flexible pipe which is relatively fine is preferably arranged in a layout having a majority of parallel sections disposed between the rows of synthetic ribbons, and attached to the top surface of the flexible backing sheet, or alternatively, is integrated into the flexible backing sheet.
The electric heating element or the flexible water pipe is integrated into the artificial surface so that relatively little energy will be wasted in heating or cooling the support substrate beneath the artificial surface. Thus, higher performance and lower operating costs are achieved. The electric heating elements or the flexible water pipes can be conveniently affixed to the artificial surface either on site or during the manufacturing process, and the costly construction of an underground system is thereby eliminated.
Other advantages and features of the present invention will be better understood with reference to preferred embodiments described hereinafter.